This invention relates to immunofluorescent assays and more particularly, to a solid phase indirect immunofluorescent (SPIIF) assay for the detection of humoral antibodies to native deoxyribonucleic acid (n-DNA).
The use of methylated bovine serum albumin (mBSA) as a carrier for nucleic acid for purposes of immunization has been known for over a decade (Plescia et al, Proc. Nat. Acad. Sci. 52, p. 279, 1964). Methylated bovine serum albumin (mBSA) has been used also in fractionating procedures for nucleic acid purification (Mandell and Hershey, Analytical Biochemistry 1, p. 66, 1960).
The formation of deoxyribonucleic acid (DNA)-methylated bovine serum albumin conjugates was first reported Plescia et al (Proc. Nat. Acad. Sci. 52, p. 179, 1964). The primary concern of these investigators was to raise antibodies to denatured (single-stranded) DNA and to smaller polynucleotides-mBSA insoluble conjugates.
Until the present invention, there has been no use of a methylated bovine serum albumin (mBSA)-native deoxyribonucleic acid (n-DNA) precipitate (i.e., conjugate) as a substrate to detect antibodies to n-DNA. Instead, authorities have advised not to use mBSA-n-DNA conjugates for immunizations. As pointed out by Plescia et al (Proc. Nat. Sci. 52, p. 279, 1964), "The mixing of mBSA with native DNA results in the formation of a compact fibrous clot that is virtually impossible to inject."
Conventional means used to detect antibodies to native DNA include radioimmunoassays (RIA) and latex agglutination tests. However, while the former means is expensive and too time consuming; the latter is rather insensitive.
In order to overcome these disadvantages, an inexpensive, sensitive means which is not time consuming is necessary. This means is provided by the present invention as set forth and described below.